The various operating branches of the Department of Defense frequently are required to clearly identify certain strategic locations with markers that are visible during both day and night. In many instances these markers will be employed rapidly in response to a particular emergency. For example, it may be necessary to mark the boundaries of a clear roadway, to identify airport runways that are operable, to locate a helicopter landing zone, to indicate certain areas where the ground conditions may be soft, cratered or strewn with debris, and a host of other possible applications. Markers of this type may be required in virtually any climactic and environmental condition, and may be subjected to physical abuse during storage, use and installation. For example, in response to certain emergency situations, markers of this type may literally be thrown from moving vehicles or hovering helicopters.
United States specification MIL-L-52543C is directed to a ground-obstruction marker light which is geared to the above described needs. The marker light described in MIL-L-52543C includes a light assembly and a ballast bag. The ballast bag of MIL-L-52543C is a reclosable bag member which is releasably attachable to the light assembly. The ballast bag is designed to accomodate approximately 20 lbs. of ballast, such as sand, rocks or any other similar material which is available in the area in which the unit would be used.
The light assembly of MIL-L-52543C is depicted and described in two acceptable alternative designs. The first design of MIL-L-52543C includes a generally cylindrical canister body, which as shown, appears to be designed for injection molding. The canister body of this first design of MIL-L-52543C is of generally truncated conical external configuration. The inside of the canister body is dimensioned to accept a six volt dry cell battery. The inside of the canister body depicted in this first design of MIL-L-52543C further includes a plurality of narrow longitudinally extending ribs, each of which includes a notch disposed at a longitudinal location corresponding to an end of a battery mounted in the canister body. The light assembly shown in the first design of MIL-L-52543C further includes an octagonal circuit board that can be retained in the notches in the narrow longitudinally extending ribs of the canister body. A light deflector, lamp and plastic dome are retained on the canister body shown in the first alternate design of MIL-L-52543C by a threaded canister cap. The lamp is electrically connected to a contact ring on the circuit board, and is activated by a three way switch (on, off and flash) which extends outwardly from the inner portion of the canister body.
A second alternative design for the light assembly shown in MIL-L-52543C includes a two part canister having a canister body for housing a six volt dry cell battery, and a canister top for housing the circuitry. The canister top and body can be threadably nested with respect to one another such that the canister top securely retains the battery in the canister body. The canister top of the second alternate shown in MIL-L-52543C flares symmetrically outwardly as it extends away from the canister body. A terminal board, deflector, lamp, gasket and dome are attached to the canister top of this second alternate by an internally threaded canister cap. The switch of the second alternate of MIL-L-52543C extends through the wall of the canister top. Thus, the symmetrical outwardly flared uppermost portion of the canister top shown in this second alternate partially protects the switch from rain and such.
Although MIL-L-52543C establishes several requirements as to performance, testing procedures, overall dimensions, and material types, it indicates that the specific illustrated figures show types of markers which have been found acceptable, but they are not intended to preclude other types of marker lights. In reviewing the known acceptable marker lights, as illustrated in MIL-L-52543C, it was observed that in many respects the light assembly portion of the illustrated markers are not adequately constructed to withstand the wide range of physical abuses to which these markers might typically be subjected. Additionally these prior art markers are not well adapted to wide range of environmental conditions in which such markers might be used.
For example, it was realized that the switch of the light assembly shown in MIL-L-52543C was improperly protected from contact and/or damage during use. Specifically, it was found that the switch was entirely exposed in one alternate design of MIL-L-52543C and only partly protected in the other alternate. Thus, if the light assembly of MIL-L-52543C is thrown from a moving vehicle, there is a substantial possibility that the switch would contact either the ground or an object on the ground thus causing the switch to either break or be urged into the wrong operational position.
It also was found that the battery was only loosely positioned in the light assembly of MIL-L-52543C such that it could be shifted out of electrical contacting position as a result of any sudden force. Similarly in the one alternative of the light assembly of MIL-L-52543C, the terminal board is only loosely positioned and as a result electrical components mounted thereon easily could be damaged. In the other alternate shown in MIL-L-52543C, the terminal board and circuitry are properly protected, but the protective housing or canister top of the assembly is extremely costly and complex to manufacturer.
The generally smooth external surface of the light assembly of MIL-L-52543C would be difficult to grasp particularly during in situ assembly, installation or maintanance. Additionally it was realized that in certain instances the area to be marked might temporarily be covered by water. This could occur, for example, if the area to be marked is a recess or crater on an airport runway, a marsh or a ditch along an edge of a road. The lights disclosed in MIL-L-52543C, however, were substantially unsuitable for use in such an environment, even for a short period of time. More particularly the prior art marker lights would evidence an inadequate degree of bouyancy in water.
In view of the above, it is an object of the subject invention to provide an improved marker light in conformance with the requirements of United States specification MIL-L-52543C.
It is another object of the subject invention to provide a marker light in which the switch is adequately protected from inadvertant contact and damage.
It is an additional object of the subject invention to provide a marker light in which the battery can be properly secured and substantially prevented from shifting.
It is a further object of the subject invention to provide a marker light in which the electric circuitry is adequately protected to avoid damage during assembly, disassembly and use.
It is still another object of the subject invention to provide a marker light which can be easily and securely grasped during assembly, disassembly and use.
It is still an additional object of the subject invention to provide a marker light with improved buoyancy.
It is yet a further object of the subject invention to provide a marker light which can be manufactured inexpensively.
It is a further object of the subject invention to provide a marker light which can be manufactured out of plastic by blow molding techniques.